A semiconductor device having a coil, which is disposed on a surface of a board and extends in a direction of normal to the surface, has been known. Such a semiconductor device is, for example, described in Japanese Patent Application Publication No. 2004-356119, which corresponds to US2004/0238929.
Such a semiconductor device is, for example, manufactured in a following manner. First, an insulation film or the like is formed on a semiconductor substrate by a spin coating technique or the like, and a frame-shaped first wiring portion is formed on the insulation film by a sputtering technique or the like. Next, a first connecting portion is formed at an end of the first wiring portion by a photolithography process and plating or the like. Then, an insulation film is deposited to surround side surfaces of the first connecting portion, by a spin coating technique or the like. Further, a second wiring portion is formed on the insulation film by a sputtering technique or the like. The second wiring portion has a frame shape, and an end of the second wiring portion is connected to the first connecting portion.
Thereafter, the step of forming the connecting portion at the end of the wiring portion, the step of placing the insulation film to surround the side surfaces of the connecting portion and the step of forming another wiring portion to be connected to the connecting portion on the insulation film are successively performed. In this way, the coil constructed of the wiring portions connected through the connecting portions is formed on the semiconductor substrate.
In such a manufacturing method, however, if the insulation film is deposited by the spin coating technique or the like, the surface of the insulation film will not be flat. Therefore, in a semiconductor device constructed by layering multiple component members each made of the wiring portion, the connecting portion and the insulation film surrounding the side surfaces of the connecting portion, an extension direction of the coil will be inclined relative to a layering direction of the component members, which is parallel to a direction of normal to the semiconductor substrate. As a result, it is difficult to obtain desirable inductance relative to the number of the wiring portions.
It is considered to flatten the surface of the insulation film by polishing or the like every after the insulation film is deposited around the connecting portion and then form the wiring portion on the flattened insulation film, so as to restrict the extension direction of the coil from inclining relative to the layering direction of the component members. In such a method, however, the number of manufacturing steps increases due to the flattening of the surface of each insulation film.